mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== The Moon [1][LINK] Luna The Moon is the only natural satellite of [2]Earth: [3]orbit: 384,400 km from Earth [jnote: radius] [4]diameter: 3476 km [5]mass: 7.35e22 kg Called [6]Luna by the Romans, [7]Selene and [8]Artemis by the Greeks, and many other names in other mythologies. The Moon, of course, has been known since prehistoric times. It is the second [9]brightest object in the sky after the [10]Sun. As the Moon orbits around the Earth once per month, the angle between the Earth, the Moon and the Sun changes; we see this as the cycle of the Moon's phases. The time between successive new moons is 29.5 days (709 hours), slightly different from the Moon's orbital period (measured against the stars) since the Earth moves a significant distance in its orbit around the Sun in that time. Due to its size and composition, the Moon is sometimes classified as a [11]terrestrial "planet" along with [12]Mercury, [13]Venus, [14]Earth and [15]Mars. The Moon was first visited by the Soviet spacecraft [16]Luna 2 in 1959. It is the only extraterrestrial body to have been [17]visited by humans. The first landing was on July 20, 1969 (do you remember where you were?); the last was in December 1972. The Moon is also the only body from which samples have been returned to Earth. In the summer of 1994, the Moon was very extensively mapped by the little spacecraft [18]Clementine and again in 1999 by [19]Lunar Prospector. The gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious is the _tides_. The Moon's gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side. Since the Earth, and particularly the oceans, is not perfectly rigid it is stretched out along the line toward the Moon. From our perspective on the Earth's surface we see two small bulges, one in the direction of the Moon and one directly opposite. The effect is much stronger in the ocean water than in the solid crust so the water bulges are higher. And because the Earth rotates much faster than the Moon moves in its orbit, the bulges move around the Earth about once a day giving two high tides per day. (This is a greatly simplified model; actual tides, especially near the coasts, are much more complicated.) But the Earth is not completely fluid, either. The Earth's rotation carries the Earth's bulges slightly ahead of the point directly beneath the Moon. This means that the force between the Earth and the Moon is not exactly along the line between their centers producing a _torque_ on the Earth and an accelerating force on the Moon. This causes a net transfer of rotational energy from the Earth to the Moon, slowing down the Earth's rotation by about 1.5 milliseconds/century and raising the Moon into a higher orbit by about 3.8 centimeters per year. (The opposite effect happens to satellites with unusual orbits such as [20]Phobos and [21]Triton). The asymmetric nature of this gravitational interaction is also responsible for the fact that the Moon rotates [22]synchronously, i.e. it is locked in phase with its orbit so that the same side is always facing toward the Earth. Just as the Earth's rotation is now being slowed by the Moon's influence so in the distant past the Moon's rotation was slowed by the action of the Earth, but in that case the effect was much stronger. When the Moon's rotation rate was slowed to match its orbital period (such that the bulge always faced toward the Earth) there was no longer an off-center torque on the Moon and a stable situation was achieved. The same thing has happened to most of the other satellites in the solar system. Eventually, the Earth's rotation will be slowed to match the Moon's period, too, as is the case with [23]Pluto and [24]Charon. Actually, the Moon appears to [25]wobble a bit (due to its slightly non-circular orbit) so that a few degrees of the far side can be seen from time to time, but the majority of the far side (left) was completely unknown until the Soviet spacecraft [26]Luna 3 photographed it in 1959. (Note: there is no "dark side" of the Moon; all parts of the Moon get sunlight half the time (except for a few deep craters near the poles). Some uses of the term "dark side" in the past may have referred to the far side as "dark" in the sense of "unknown" (eg "darkest Africa") but even that meaning is no longer valid today!) The Moon has no atmosphere. But evidence from [27]Clementine suggested that there may be water ice in some deep craters near the Moon's south pole which are permanently shaded. This has now been [28]confirmed by [29]Lunar Prospector. There is apparently ice at the north pole as well. The cost of future lunar exploration just got a lot cheaper! The Moon's crust averages 68 km thick and varies from essentially 0 under Mare Crisium to 107 km north of the crater Korolev on the lunar far side. Below the crust is a mantle and probably a small core (roughly 340 km radius and 2% of the Moon's mass). Unlike the Earth, however, the Moon's interior is no longer active. Curiously, the Moon's center of mass is offset from its geometric center by about 2 km in the direction toward the Earth. Also, the crust is thinner on the near side. There are two primary types of terrain on the Moon: the heavily cratered and very [30]old _highlands_ and the relatively smooth and younger [31]maria. The maria (which comprise about 16% of the Moon's surface) are huge impact craters that were later flooded by molten lava. Most of the surface is covered with regolith, a mixture of fine dust and rocky debris produced by meteor impacts. For some unknown reason, the maria are concentrated on the near side. Most of the craters on the near side are named for famous figures in the history of science such as [32]Tycho, [33]Copernicus, and [34]Ptolemaeus. Features on the far side have more modern references such as Apollo, Gagarin and Korolev (with a distinctly Russian bias since the first images were obtained by [35]Luna 3). In addition to the familiar features on the near side, the Moon also has the huge craters _South Pole-Aitken_ on the far side which is 2250 km in diameter and 12 km deep making it the the largest impact basin in the solar system and _Orientale_ on the western limb (as seen from Earth; in the center of the image at left) which is a splendid example of a multi-ring crater. A total of 382 kg of rock samples were returned to the Earth by the [36]Apollo and [37]Luna programs. These provide most of our detailed knowledge of the Moon. They are particularly valuable in that they can be dated. Even today, more than 30 years after the last Moon landing, scientists still study these precious samples. Most rocks on the surface of the Moon seem to be between 4.6 and 3 billion years old. This is a fortuitous match with the oldest terrestrial rocks which are rarely more than 3 billion years old. Thus the Moon provides evidence about the early history of the Solar System not available on the Earth. Prior to the study of the Apollo samples, there was no consensus about the origin of the Moon. There were three principal theories: _co-accretion_ which asserted that the Moon and the Earth formed at the same time from the [38]Solar Nebula; _fission_ which asserted that the Moon split off of the Earth; and _capture_ which held that the Moon formed elsewhere and was subsequently captured by the Earth. None of these work very well. But the new and detailed information from the Moon rocks led to the _impact_ theory: that the Earth collided with a very large object (as big as Mars or more) and that the Moon formed from the ejected material. There are still details to be worked out, but the impact theory is now [39]widely accepted. The Moon has no global magnetic field. But some of its surface rocks exhibit remanent magnetism indicating that there may have been a global magnetic field early in the Moon's history. With no atmosphere and no magnetic field, the Moon's surface is exposed directly to the [40]solar wind. Over its 4 billion year lifetime many hydrogen ions from the solar wind have become embedded in the Moon's regolith. Thus samples of regolith returned by the Apollo missions proved valuable in studies of the solar wind. This lunar hydrogen may also be of use someday as rocket fuel. More about the Moon * more [41]Moon images * from [42]LANL * from [43]RPIF * from [44]StarDate * from [45]RGO * from [46]NSSDC * from [47]NASA Spacelink * a [48]Teacher's Guide to the Moon (concentrating on lunar geology) * [49]Lunar rocks and regolith * [50]Io and Luna, a comparison from LANL * [51]Life Under the Moon, from Phil Plait's excellent [52]Bitsize Astronomy site * Why the Moon [53]looks bigger near the horizon * a longer explanation of the [54]tides and their causes and effects * [55]leap seconds and the slowing of the [56]Earth's rotation * [57]historical info about observations of the Moon * [58]Lunar Meteorites * [59]Moon Phases explained * The impact theory of lunar formation + [60]The Origin of the Moon, with nice paintings by Dr. William K. Hartmann + brief segment from [61]Earth and Sky + [62]The Origin of the Earth and Moon, written by G. Jeffrey Taylor, Hawaii Institute of Geophysics and Planetology + [63]Big Bang, New Moon (from Southwest Research Institute) + [64]New theory links moon's current orbit to its formation via a giant impact (from Southwest Research Institute) * lunar exploration + [65]Exploring the Moon from [66]LPI, nice images from Lunar Orbiter and others plus lots of explanatory text + Apollo info and images [67]html + [68]Apollo Missions + [69]Scientific Discoveries Made During Apollo + [70]Apollo 11 at Twenty-Five (ExInEd Hypercard stack) + [71]Planetary Missions and Materials Exploration Server + [72]Clementine - DSPSE (including some nice images) + [73]Lunar Prospector + [74]LunarSat, the first European lunar mission + [75]The Artemis Project, a private venture to establish a permanent, self-supporting community on the Moon! + [76]LunarSat + [77]Yes, we really did go to the Moon, debunking the Moon Hoax theories * Ice on the Moon + [78]Lunar Prospector Special Report + [79]Eureka! Lunar Prospector finds ice + [80]article on lunar ice + another article on [81]lunar ice + 2nd major report from Lunar Prospector * [82]Lunar Nomenclature Table * [83](Earth and) Moon Viewer * [84]Transient Lunar Phenomena * [85]Inconstant Moon by John Walker, info about the Moon's changing appearance * [86]Inconstant Moon by Kevin Clarke, for amateur astronomers * [87]Lunar Info for the Amateur Astronomer * [88]Names of the Full Moons * The [89]Lunar size illusion, why the Moon looks bigger near the horizon * [90]The Triple Triumph of the Moon by Isaac Asimov * [91]The Face of the Moon, an exhibit of rare books and maps from the Linda Hall Library * fiction + [92]The Moon in Science Fiction, a huge bibliography + [93]From the Earth to the Moon, fiction by Jules Verne + [94]Chinese Moon Legends * [95]Eugene M. Shoemaker: A Timeless Tribute Open Issues * Why are the maria concentrated on the near side? * Why is the Moon's center of mass off center? Because of the tidal lock with the Earth? * Now that we've found water on the Moon, what are we going do to with it? * Only twelve men have ever walked on the surface of the Moon. Who will be the 13th? Who will be the first woman? _________________________________________________________________ _Express_ to [96]Mars [97]Contents ... [98]Earth ... Moon ... [99]Mars ... [100]Data [101]Host _________________________________________________________________ [102]Bill Arnett; last updated: 2003 Jan 12 References Visible links 1. http://www.seds.org/billa/pics/Luna2.jpg 2. http://www.nineplanets.org/earth.html 3. http://www.nineplanets.org/data.html 4. http://www.nineplanets.org/data1.html 5. http://www.nineplanets.org/data1.html 6. http://www.pantheon.org/articles/l/luna.html 7. http://www.pantheon.org/articles/s/selene.html 8. http://www.pantheon.org/articles/a/artemis.html 9. http://www.nineplanets.org/datamax.html#brightest 10. http://www.nineplanets.org/sol.html 11. http://www.nineplanets.org/overview.html#ter_p 12. http://www.nineplanets.org/mercury.html 13. http://www.nineplanets.org/venus.html 14. http://www.nineplanets.org/earth.html 15. http://www.nineplanets.org/mars.html 16. http://www.nineplanets.org/spacecraft.html#luna2 17. http://www.nasm.edu/APOLLO/ 18. http://www.nineplanets.org/spacecraft.html#clementine 19. 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file://localhost/www/sat/files/planets/luna.html#formation 40. http://www.nineplanets.org/sol.html#solarwind 41. http://www.nineplanets.org/pxmoon.html 42. http://www.solarviews.com/eng/moon.htm 43. http://www.nasm.edu/ceps/rpif/moon/rpifmoon.html 44. http://stardate.utexas.edu/resources/ssguide/moon.html 45. http://www.nmm.ac.uk/site/navId/00500300f00k 46. http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-moon.html 47. http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Our.Solar.System/Earth's.Moon/.index.html 48. http://lunar.arc.nasa.gov/education/tg/teach1.html 49. http://www-curator.jsc.nasa.gov/curator/lunar/lunar.htm 50. http://www.solarviews.com/eng/edu/moonio.htm 51. http://www.badastronomy.com/bitesize/solar_system/moon.html 52. http://www.badastronomy.com/bitesize/index.html 53. http://www.badastronomy.com/bad/misc/moonbig.html 54. http://www.badastronomy.com/bad/misc/tides.html 55. http://tycho.usno.navy.mil/leapsec.html 56. http://maia.usno.navy.mil/eop.html 57. http://es.rice.edu/ES/humsoc/Galileo/Things/moon.html 58. http://epsc.wustl.edu/admin/resources/moon_meteorites.html 59. http://aa.usno.navy.mil/faq/docs/moon_phases.html 60. http://www.psi.edu/projects/moon/moon.html 61. http://earthsky.com/1998/esmi980929.html 62. http://www.psrd.hawaii.edu/Dec98/OriginEarthMoon.html 63. http://www.swri.org/3pubs/ttoday/spring99/moon.htm 64. http://www.swri.org/9what/releases/incline.htm 65. http://www.lpi.usra.edu/pub/expmoon/lunar_missions.html 66. http://www.lpi.usra.edu/lpi.html 67. http://www.nasm.edu/APOLLO/ 68. http://www.lpi.usra.edu/pub/expmoon/apollo_landings.html 69. http://www.nasm.edu/apollo/apollotop10.htm 70. http://marvel.stsci.edu/exined-html/Apollo.html 71. http://www-sn.jsc.nasa.gov/explore/explore.htm 72. http://www.nrl.navy.mil/clementine/clementine.html 73. http://lunar.arc.nasa.gov/ 74. http://lunarsat.lrt.mw.tu-muenchen.de/ 75. http://www.asi.org/ 76. http://www.lunarsat.de/ 77. http://www.badastronomy.com/bad/misc/apollohoax.html 78. http://lunar.arc.nasa.gov/science/results/lunarice/index.html 79. http://lunar.arc.nasa.gov/science/results/lunarice/eureka.html 80. http://www.ae.utexas.edu/~tsgc/info/lunarice.html 81. http://nssdc.gsfc.nasa.gov/planetary/ice/ice_moon.html 82. http://wwwflag.wr.usgs.gov/USGSFlag/Space/nomen/moon/moonTOC.html 83. http://www.fourmilab.ch/earthview/vplanet.html 84. http://www.geocities.com/CapeCanaveral/Launchpad/1837/ 85. http://www.fourmilab.ch/earthview/moon_ap_per.html 86. http://www.inconstantmoon.com/index.htm 87. http://www.seds.org/billa/psc/lunam.html 88. http://www.nineplanets.org/../psc/fullmoons.html 89. http://www.research.ibm.com/resources/news/20000103_moon_illusion.shtml 90. http://magna.com.au/~prfbrown/i_asimov.html 91. http://www.lhl.lib.mo.us/pubserv/hos/moon/cover.htm 92. http://www.bibliography.com/moon/ 93. gopher://wiretap.spies.com/00/Library/Classic/moon.jv 94. http://peacock.tnjc.edu.tw/MOON/moon.html 95. http://condor.lpl.arizona.edu/~carolyn/tribute.html 96. http://www.nineplanets.org/mars.html 97. http://www.nineplanets.org/nineplanets.html#toc 98. http://www.nineplanets.org/earth.html 99. http://www.nineplanets.org/mars.html 100. http://www.nineplanets.org/data.html 101. http://www.nineplanets.org/host.html 102. http://www.nineplanets.org/../arnett.html Hidden links: 103. ftp://seds.lpl.arizona.edu/pub/images/apollo/old/misc/footprint.gif 104. http://www.jpl.nasa.gov/galileo/images/earthmo2.gif 105. http://www.solarviews.com/cap/moon/farside.htm 106. http://www.jpl.nasa.gov/galileo/images/bwmoon.html 107. http://nssdc.gsfc.nasa.gov/image/planetary/moon/gal_moon_color.jpg 108. http://pds.jpl.nasa.gov/planets/gif/ear/igneous.gif 109. http://www.nasm.edu/apollo/AS17/images/LanderScene.jpg 110. http://www.geophys.washington.edu/SPACE/gif/earthr2.gif 111. http://www.sciencemag.org/cgi/content/abstract/281/5382/1496 112. http://images.jsc.nasa.gov/images/pao/AS11/10075267.jpg